To add in my two cents, I think it would be good for SAM to be a DPS job, primarily due to armor.

Right now, we have several sets of armor assigned to a variety of different jobs.

Fending (Tank) -> PLD, WAR, DRK
Maiming (High DEF DPS) -> DRG
Striking (STR Melee DPS) -> MNK
Scouting (DEX Melee DPS) -> NIN
Aiming (DEX Ranged DPS) -> BRD, MCH
Casting (INT Ranged DPS) -> BLM, SMN
Healing (Healer) -> WHM, SCH, AST

The way I look at this is, basically, all of the different roles in the game right now. If they make up more roles, then we'll see.

There were three jobs added in Heavensward: DRK, MCH, and AST, as well as a special job in 2.4, NIN.

Because of this, I do not think we will see any job that uses Fending, Aiming, Healing, or Scouting gear in 4.0. And assuming there are three jobs introduced, that just leaves Maiming, Striking, and Casting to get new jobs associated with them.

SAM would perfectly adapt to Maiming gear, quite easily in fact, as it is heavier armor than Striking/Casting.

I predict RDM will wear Casting gear, as it will likely be an INT Melee DPS of some sort (unless I am dead wrong, which is entirely plausible)

As for Striking Gear... it would have to be a job that wouldn't look out of place in Striking Gear (then again, MCH look somewhat out of place in some BRD gear, so that may be wrong)... maybe a job that uses chakram for weapons? That'd be pretty cool!